This invention relates to power transmission belts and, more particularly, to an improved V-ribbed belt having an outer back-side surface with a high coefficient of friction for driving flat-faced back-side pulleys.
V-belts and V-ribbed belts are used in a wide range of environments. V-ribbed belts are preferred for their high power transmission capability, which is attributable to the large contact area between the ribs on the belt and the flank on the cooperating pulleys.
In operation, there is a tendency for V-belts and V-ribbed belts to emit noise; a common complaint, especially on automotive drives. Belt noise is predominately the result of pulley engagement and disengagement noise arising as the ribs on the belt enter into and exit from the pulley grooves or arising from excessive rotational slip of the pulley relative to the belt. Rotational slip occurs during rapid acceleration or deceleration of the drive such as is encountered during shifting, engine startup or engine shutdown or due to excessive loading or insufficient wrapping around the pulleys.
Previous attempts to reduce belt noise and reduce rotational slipping of back-side pulleys were successful for the drive systems of that time. However, current drive systems are increasingly incorporating pulleys on the back-side of the belt to drive accessories like fans, water pumps, air conditioners and the like. With these increased performance requirements on engines, the load on such accessories has increased beyond the current capabilities of existing serpentine belts. As such, improved V-ribbed belts are needed to drive back-side pulleys efficiently under such loads. The V-ribbed belt should also reduce noise and slippage.